1. Field of the Invention
The present invention relates in general to devices for powering a drill string into subterranean strata and more specifically to such devices that have a pivoting drill head assembly.
2. Description of the Prior Art
Soil drilling devices are typically mounted on a trailer or the bed of a truck to provide for their ready portability from one working location to another. Also, they include a vertically alignable mast assembly that may be pivotable into a horizontal position for travel of the device between locations. A drill head is normally mounted on the mast assembly for vertical movement thereon and includes a rotary power drive for applying rotational force on the end of a drill string being driven into the ground.
To begin a drilling operation with such drilling devices, the drill head is moved to the top of the mast, and a drill rod is placed in a rod handling means located at the bottom of the mast and is then attached to the drill head. A wide variety of methods have been employed in the past for placing the drill rod into the rod handling means, but it has been found that one of the simplest procedures for accomplishing this operation is by means of a hoist winch having hoist sheaves placed at the top of the mast. However, because of the normal position of a drill head on the mast interposed between the hoist sheaves and the rod handling means, it presents an obstruction to easy handling of the drill rod.
There have been several solutions proposed for moving the drill head out of an obstructing position when it is desired to add or remove the string rod with the hoist winch. The most practical method for moving the drill head from an obstructing position is to pivotally mount the drill head on the drill mast so that when desired, the drill head may be pivoted to one side of the mast into an unobstructing position as described in U.S. Pat. No. 3,835,940 issued Sept. 17, 1974. During normal operation of the device of such patent, a latch assembly is employed to hold the drill head from pivoting out of position.
On drilling devices having short mast sections, unlatching and pivoting of the drill head can be accomplished manually by a worker standing on the ground. However, on drilling devices having mast sections over ten feet in length, it is necessary for the worker to climb the mast for unlatching and pivoting operation or else separate hydraulic cylinders are employed for the tasks of unlatching the drill head and then pivotally moving the head out of an operating position. It has been found that for efficient drilling operation, manual movement of the drill head is highly undesirable and yet the use of two separate hydraulic cylinders is unduly expensive. Accordingly, the present invention provides a rotary drilling device having a single power means for automatically unlatching the drill head for pivotal movement thereof out of an operating position, for returning the drill head back into the operating position and relatching of the drill head.